1. Field of the Invention
This disclosure relates to a current limiting type circuit breaker, and particularly, to a movable contactor assembly for the current limiting type circuit breaker.
2. Background of the Invention
A current limiting type circuit breaker includes stationary contactors each having a “U” shape and has a configuration that an incoming current direction via the stationary contactor and an outgoing current direction via a movable contactor are opposite to each other. Hence, the structure of the current limiting circuit breaker is suitable for performing a current limiting operation that when a large fault current, such as a short-circuit current, flows on a circuit, the electromagnetic forces generated around the movable contactor and the stationary contactor cause electromagnetic repulsive forces and accordingly the movable contactor is automatically separated from the stationary contactor to limit the current flow amount.
In the current limiting circuit breaker, a movable contactor having a double-contacts structure having contacts at both ends thereof is being frequently used because the movable contactor having the double-contacts structure allows for a faster current limiting operation by virtue of a stronger electromagnetic repulsive force than a movable contactor with a single-contacts structure.
In addition to the current limiting operation, for maintaining a contact state between the movable contactor and the stationary contactor while a normal current flows on a circuit, a movable contactor assembly in the current limiting circuit breaker includes springs for providing contact pressure to the movable contactor, and connection pins for transferring elastic forces of the springs to the movable contactor.
An example of the related art movable contactor assembly in the current limiting circuit breaker may be Korean Patent Application No. 10-0574788 (Title of the Invention: Contactor Assembly for Circuit Breaker) filed by the applicant of this disclosure.
The related art provides a movable contactor assembly having a self-centering structure of supporting a movable contactor at a shaft without a movable contactor center pin. This is a configuration of guiding the contact pin which moves to a current limiting position or a contact position. The configuration has a characteristic that a pair of cam plates are installed on an inner wall of the shaft.
However, the related art movable contactor assembly includes a roller for smooth friction between the cam plates and the contact pin, a pair of springs disposed on each one surface of the shaft, links, the cam plates and the like. The complicated structure and many components lower assembly productivity and increase fabricating costs. Furthermore, erroneous operations, such as torsion or separation, are caused after assembling those many components due to accumulation of air gaps among those many components.
As another example of the related art movable contactor assembly for the current limiting circuit breaker may be Korean Registered Patent No. 10-0606424 (Title of the Invention: Movable contactor assembly for Current Limiting Circuit Breaker) filed and registered by the applicant of this disclosure.
In order to maintain a movable contactor in a state separated from a stationary contactor by a current limiting operation until performing a trip operation by a trip mechanism and a switching mechanism, the related art movable contactor assembly according to the Korean Registered Patent No. 10-0606424 includes contact plates for transferring elastic forces of springs to the movable contactor, and a convex portion having a flat surface and a curved surface for providing a guide surface of the contact plates to the movable contactor.
The related art movable contactor assembly according to the Korean Registered Patent No. 10-0606424 especially has a center shaft of the movable contactor installed for preventing a rotation center of the movable contactor from being moved during a current limiting operation in a self-centering structure.
However, in the another example of the related art, a pair of springs are disposed for each one surface of the movable contactor at both sides based on the center shaft for prevention of interference and balancing between the center shaft and the springs. A pair of supporting pins for each one surface of the movable contactor are also disposed to support one end of each spring. With regard to this configuration, the many number of springs and spring supporting pins lower assembly productivity and increase fabricating costs.